Monday, Sept. 17 Measuring effectiveness and other CEA considerations

1Schneider Institute for Health PolicyHeller Graduate SchoolBrandeis UniversitySeptember 2001

by Donald S. Shepard, Ph.D.

Schneider Institute for Health PolicyHeller School, MS 035Brandeis University

Waltham, MA 02454-9110 USA

Tel: 781-736-3975 • Fax: 781-736-3965Web: http://www.sihp.brandeis.edu/shepard

E-mail: [email protected]

Monday, Sept. 17Measuring effectiveness and other CEA

considerations


Practical information

• Teaching assistant: [email protected]

• Administrative assistant: Linda Purrini, Next to library in Heller

781-736-3930

[email protected]

• Cost of packet: $6.00


Donald S. Shepard, Ph.D.Schneider Institute for Health Policy

Heller School, MS 035Brandeis University

Waltham, MA 02454-9110 USA

Tel: 781-736-3975 • Fax: 781-736-3965Web: http://www.sihp.brandeis.edu/shepard

E-mail: [email protected]

Measuring Effectiveness and Outcomes, QALYs and DALYs


Outline

• Types of indexes

• Measuring national disease burden

• Health status questionnaires


Needs for combining length and quality of life

• Assessing the disease burden of a country or a region, to see which health problems are greatest, and how one country or region compares with another.

• Evaluating a program that may impact both mortality and morbidity.


Indexes for combining length and quality of life

• Quality Adjusted Life Years, QALYs (Zeckhauser and Shepard, 1976)

• Potential Days of Life Lost, PDLLs (Ghana health assessment team, 1980)

• Disability Adjusted Life Years, DALYs (World Development Report, 1993)


Types of scales for assessing quality of life

• Value scale: a measure of preferences on a scale with arbitrary endpoints (example, SF36, scale of 0 to 100).

• Utility scale: a measure of preferences on a scale with endpoints of 0 and 1 and spacing consistent with probability theory.


Burden of disease


Ways of assessing utilities

• Probability approach – breakeven probability

• Time tradeoff - breakeven time


General health question

In general, would you say your health is poor, fair, good, very good, or excellent?1 poor2 fair3 good 4 very good5 excellent


Limitation of physical activities

Here are a list of activities that you might do during a typical day.

How much does your health limit you right now in moderate activities, such as moving a table, pushing a vacuum cleaner, bowling, or playing golf?

1 A lot2 A little3 Not at all


Limitation of social activities

During the past 4 weeks, how much of the time has your physical health or emotional problems interfered with your social activities like visiting with friends or relatives? 1 All of the time2 Most of the time3 A good bit of the time4 Some of the time5 A little of the time6 None of the time


Time tradeoff

• Time tradeoff - find the breakeven time• Suppose we were to live 10 years with an

impaired state, I• Instead, we could live Y years with perfect

health.• Suppose the the value y would make us just

indifferent.• Then the utility of I is y / 10.• E.g., if y is 7, then the utility is 7/10 = 0.70


Von Neumann – Morgenstern Utility 1

• Suppose we have a “good” outcome which has a utility of 1 (e.g. living year in perfect health)

• Bad outcome has a utility of 0 (e.g. dying at the start of the year)

• Intermediate outcome (I) has utility of x (e.g. living with a health limitation), x = u(I)


Von Neumann – Morgenstern Utility 2

• Suppose I is indifferent between probability p of good outcome, and 1-p of bad outcome

• The utility is von Neumann-Morgernstern if x equals p.


Illustration: gastroenteritis in Ghana,c. 1980


Remaining life expectancy by age, Ghana (1968)

47

5451

4743

3935

3127

2420

1714

11 8 6 4

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Age

Rem

aini

ng li

fe e

xpec

tanc

y


Disease burden for gastroenteritis (1): Mortality loss burden per death

Days lost per death =

Remaining life expectancy (years) at age of death

52.8

x Days per year 365.25

= Days lost per death 19,285


Disease burden for gastroenteritis (2): Mortality loss burden per case

Days lost per case from mortality =

Case fatality rate 0.01

x Days lost per death 19,285

= Days lost per fatal case 192.85


Disease burden for gastroenteritis (3): Morbidity loss burden per case

Days lost per non-fatal case =

Average duration per surviving case (days)

14

x Proportion surviving 0.99

= Days lost per non-fatal case 13.86


Disease burden for gastroenteritis (4): Total burden per case (days)

Total days lost per case =

Days lost per fatal case 192.85

+ Days lost per non-fatal case 13.86

= Days lost per case 206.71

Note: Mortality share

(% from fatal cases) 93%


Disease burden for gastroenteritis (5): Total annual burden per 1000 persons

Total annual burden per 1000 persons =

Total burden per case 206.71

x Number of new cases per year (incidence)

70

= Total annual burden per 1000 persons

14,470


Extensions:Discounting of health impacts

• Impacts in future years should be discounted, just as money is discounted

• Discounting arises due to “time preference”:– We are anxious to get good things soon.– If we have to wait, them “good” is less highly

valued now.


Discount factors

PERIODS0 1 2 3

Expect flow of "life" (years) 1.00 1.00 1.00 1.00

Disc. Rate 0.03 0.03 0.03 0.03

Disc factor 1.000 0.971 0.943 0.915

PV 1.000 0.971 0.943 0.915


Graph of discount factors (at 3%)

0.00.10.20.30.40.50.60.70.80.91.0

0 10 20 30 40 50 60 70Years from now

Dis

co

un

t fa

cto

r


Table of DALYsLifespan DALYs

0 0.0010 8.5320 14.8830 19.6040 23.1150 25.7360 27.6870 29.1280 30.2090 31.00

100 31.60


DALYs from a life of specified number of years

9

15

20

2326

2829 30 31 32

00

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90 100

Years

DA

LY

s


Disease burden exercise

• Illustrate the calculation of PDLLs from exercise on web site

• http://www.sihp.brandeis.edu/shepard

Monday, Sept. 17 Measuring effectiveness and other CEA considerations

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